Rotary compressor for refrigerating apparatus



May 23, 1939. R. M. sMrrH 2,

ROTARY comrnnsson FOR REFRIGERATING APPARATUS Filed March 51, 1936 2 Sheets-Sheet 1 IN VENTOR.

ATTORNEYS May 23, 1939. R. M. SMITH "2,159,936

ROTARY COMPRESSOR FOR REFRIGERATING APPARATUS Filed March 51, 1936 2 Sheets-Sheet 2 Patented May 23,. 19 39 PATENT OFFICE ROTARY COMPRESSOR FOR REFRIGERAT- ING APPARATUS Rolf M. Smith, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporatlon of Delaware Application March 31, 1936, Serial No. 71,869

6 Claims.

This invention relates to refrigerating apparatus and more particularly to refrigerant compressors and pumps.

Rotary pumps and compressors are now widely I used for pumping liquids and gases including refrigerants. In such pumps a rotary member is ordinarily provided within the cylinder which describes a path which extends around the interior of the cylinder with a relatively small 10 clearance. It has been customary to make this clearance uniform throughout the entire pumping or compression stroke regardless of the fact that the pressure differences vary considerably throughout the stroke and generally are at a 15 low value at the beginning of the stroke and at a relatively high valuebeginning with the last two-thirds or three-fourths of the stroke. There- 4 fore, if the pump had a relatively large amount of clearance the efliciency would be considerably g -reduced.

. It is an object of my invention to adjust the clearance generally according to the local pressure differences which exist in such a pump.

It is another object of my invention to pro- 35 vide an improved method of and means for adjusting the clearance in the portion of the stroke where the higher pressure differences and the higher fluid density exist.

It is still another object of my invention to so provide a two stage rotary compressor having the advantages of simplicity, ease of manufacture, and a minimum of parts.

In a two stage rotary compressor, it has also been customary to make the clearance in both stages uniform regardless of the fact that the .j pressure difljerences in the higher stage are; \greater and that leakage in the higher stage is a more serious consideration'than in the lower stage. Y o It is an object of my invention to provide a rotary compressor of the two stage type in which the clearance in the higher stage is less than the clearance in the lower stage. n It is another object of my invention to proing the clearance in the portions of rotary compressors which require greater accuracy in achieving a minimum clearance.

Further objects and advantages of the present invention will be'apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

, In the drawings:, 56 Fig. 1 is a vertical sectional view taken along pumping chamber is outlet and a flapper valve which permits the disvide an improved means and method for adlustsentation of the remainder of the refrigerating system;

Fig. 2 is a fragmentary sectional view taken along the line 22 of Fig. 1; I

Fig. 3 is a fragmentary sectional view taken along the line 33 of Fig. 2;

Fig. 4 is an exaggerated diagrammatic view showing the customary clearances provided in the stages of a two-stage rotary compressor; and

Fig. 5 is a'view similar to Fig. 4 but with the clearances properly adjusted in an exaggerated form according to my invention.

Briefly, I have disclosed a sealed unit typeof rotary refrigerant compressor having an eccentric roller type of rotor and a plurality of divider blocks positioned about 120 from each other, which divides the space between the rotor and its cylinder into two pumping chambers of which the lower pressure chamber extends through an arc of approximately 240 while the higher pressure chamber extends through an arc of approximately 120. The low pressure chamber is provided with an inlet in the usual position adjacent one of the divider blocks and an outlet ad'- jacent the other divider block provided'wlth a flapper valve housed within the chamber which communicates with the inlet of the high pressure pumping chamber. The high pressure likewise provided with an charge of the compressed gas into the interior of the sealed unit.

The outlet from the sealedunit is through a hollow stationary shaft which serves to support the hollowrotary drive shaft. The compressed gas from this outlet is conducted to the plate type condenser where it is liquefied and forwarded to an evaporator means where it evaporates and is returned to the inlet of the large pumping chamber in vapor form.

. The wall of the cylinder is provided with 2. lateral screw thread adjusting means for adjusting its position laterally so that the clearance in;

the high pressure chamber may be made less than that in the low pressure chamber. In order todo this conveniently, the screws which nor- A mally anchor the cylinder or the? high pressure portion thereof, may be loosened slightly and, provided with a rather loose fit in the cylinder so that the clearance in the high pressure chamber may be readily adjusted to a desired fixed value. k I

Referring now more particularly to the drawings, there is shown a motor-compressor unit generally designated by the reference character 20 for compressing refrigerant and for forwarding the compessed refrigerant to a flat plate type condenser 22 where the compressed refrigerant is liquefied and forwarded through a conduit 26 under the control of an expansion control device 26 to an evaporating means 28 located within a compartment 35 containing a medium to be cooled. The refrigerant evaporates within the evaporating means and is returned to the inlet of the compressor through a return conduit 32.

The operation of the motor-compressor unit is controlled by a snap acting switch it operated according to the temperature of a thermostatic bulb mounted upon the evaporating means and located in electrical series circuit relationship with the stator :36 of an electric driving motor which includes the rotor 35.

The compressor includes an inverted outer cup shaped casing member M? which has a lower flange or rim which receives a flanged bottom member Q2 provided with a metal seal it between the extermitles ofthe flanges. Between this inverted cup shaped member 68 and the bottom plate is a vertical hollow stationary shaft 4% which serves as the outlet for the compressed gas.

. A hollow drive shaft 38 is rotatably mounted upon the stationary vertical shaft it and carries the rotor at its upper end while at its lower end, it is provided with an eccentric portion 55 which has a roller 52 rotatably mounted thereon which, together with the eccentric portion 59, serves as the rotor or impeller of the compressor. This roller 52 revolves about the axis of the stationary shaft 68 within the cylindrical housing 5 3.

Beneath the cylinder 5d and the roller 52 is a V hardened ground steel plate 5'6 which has beneath it a second plate 58 of somewhat softer metal which is welded or otherwise secured to the flat center portion or the bottom plate ii. ihe cylinder is fastened to the plate 58 by cap or machine screws 6B which extend through relatively large holes in the cylinder. Above the cylinder 5G and the rotor 52 is provided a second plate 62 of hardened ground steel provided with a second plate $6 of softer steel above it. These two plates are fastened to the cylinder by the screws 66. Extending through gaps or slots in the" ing chamber 72 is located immediately adjacent the divider block W in a clockwise direction therefrom' This opening extends down through the plates 56, 58 and Q2 and is provided witha threaded coupling member it upon the bottom of the sealed unit for connection with the return conduit 32. The outlet of this low pressure pumping chamber i2 is provided by an aperture in the plate 62 which opening is provided with a hardened face member which has its upper flanged edge serving as a valve seat for a flapper discharge valve 82 located in a chamber 86 provided in the upper plate 64, which chamber is closed at its top by an additional plate member 86. This flapper valve is provided with a heavy steel guard member 9B which with the flaps -ferential portions of the compressor.

arcacee per valve is fastened to the plate 62 by screws at the fixed end. This guard member mounting serves to prevent excessively wide opening of the flapper valve and thus prevents it from being stressed excessively and thereby prevents it from breaking on account of fatigue stress.

This chamber 84 is located above the divider block 68 and has its inlet opening 80 upon the counterclockwise side of the divider block 68 while it has its outlet opening 88 within the plate 62 upon the opposite side of the divider block 68 leading directly into the inlet end of the smaller pumping chamber 76. At the opposite end of the small pumping chamber Hi, there is provided a discharge opening and a flapper valve 92. It discharges into the interior of the sheet metal member which surrounds the upper portion of the compressor. This sheet metal member in cooperation with the drive-shaft 38 provides a space and a sort of a labyrinth path for separating the refrigerant from the oil or lubricant 96 provided in the bottom portion of a compressor. This casing also provides an anchor for the divider block springs 98 which extend into drilled recesses in each of the divider blocks 88 and 75 in order to hold the inner surface of the divider block against the roller 52.

The two sections of the cylindrical wall 5% are held together by'the screws 65 and the top plates 62 and t l. This unit is held in place normally by the cap or machine screws $5 which extend through rather large holes in the wall 55. so that the screws may be loosened slightly and the wall positioned in order to provide whatever clearance is desired. It has heretofore been customary to maintain a uniform rotor clearance throughout the stroke of the rotor in a rotary compressor. There is, however, a greater tendency to leakage during the final portions of the stroke in a single-stage compressor and during the final stages in a multi-stage compressor.

I propose to make this clearance less than in final stages of a single stage compressor, as well as in the final stage of a multi-stage compressor. This is illustrated diagrammatically in Figs. 4 and 5, wherein there is provided a cylindrical wall Hi3 provided with divider blocks H2 and H54. Within the cylinder is a rotor H6 mounted eccentrically upon the drive shaft M8. It will be seen that the clearance in the second stage pumping chamber I28 is substantially the same as indicated by the dotted line I 22 in the lower stage 52d. According to my invention I adjust theposition of the cylindrical wall ill) so that clearance at .the high pressure pumping chamber I2!) is less than the clearance in the larger low pressure pumping chamber flZd as indicated by the dotted line 826. This naturally reduces leakage in the high pressure pumping chamber and has little efiect upon the leakage in the low pressure pumping chamber because of its larger volume.

Thus, I- propose to make the cylindrical wall adjustable so that the clearance may be readily adjustable to obtain improved performance of the compressor, particularly by reducing the clearance in the higher pressure or pressure dif- In addition to this. however, I have also provided a means forreadily making this form of lateral adjustment conveniently and accurately. In order to do this, I have provided a bracket l30 fastened to the flanged bottom plate 42. This bracket 13%] rotatably supports the head I32 of an adjusting screw I35 which is threaded into a threaded aperture 13% extending in a radial direc clearance as needed in thehigh pressure portions of the low pressure pumping chamber, as

7 well as the high pressure pumping chamber.

In the form of invention shown in the drawings, there are at least two different ways in which this might be done. In the first place, it should be noted that the cylindrical wall 54 is divided'into two wholly separate parts by the divider blocks 68 and 10 which are in the proportions of about 240 and 120.

In one way, the adjustment is made before the.

application of the upper plates 82 and 64, and the larger or 240 part of the wall 54 is anchored concentrically with the vertical stationary shaft 42. The 120 portion of the wall 54 is adjusted by the screw I34 to the desired clearance independently and without any reference to the clearance or location of the 240 portion of the wall 54. The 120 portion is then fastened in place permanently by screws 60 and divider blocks of the proper size are provided between the gaps in the cylindrical wall 54. This may be done by selective assembling. Thereafter, the upper plates 62 and 64 are fastened in place. v

The second way may be used where it is desired to adjust the. clearance by placing the entire cylindrical wall including the 120 and the 240 parts eccentrically of the stationary vertical shaft 46. To do this the two parts may be first assembled concentrically and then held together by fastening the upper plates 62 and 64 by the screws 65. Then this assembly may be adjusted to an eccentric position with the desired clearance in the second stage obtained by the adjustment of the screw I34.

In a single stage compressor, the cylindrical wall is in one horseshoe shaped piece and this may be readily adjusted eccentrically either beforeor after the application of the top plates 62 and 64 by a screw adjustment like that provided by the screw I34. After the adjustment is ob-.

tained the wall is permanently fastened in place.

However, it is preferred to do this before the plates 62 and 64 are applied.

It is deemed most desirable, however, to ad-' just the cylindrical wall 54 so as to maintain a.

predetermined clearance in. the high pressure pumping chamber and in the final portion of the low pressure pumping chamber and to permit the manufacturing variations to occur in the low pressure portion of the first stage pumping chamber. After thedesired adjustment is obtained, a lock nut I38 upon the screw I34 may be tightened to hold the adjustment and thereafter-the screws 60 may be tightened to fix the cylindrical wall in place with respect to the axis of the drive shaft 48 so as to preserve the clearance to which the compressor has been adjusted. After this posltionha's been fixed, if desired, the screw I34 as well as the lock nut may be removed, thus making use of this feature somewhat as a fixture. This provides a very simple inexpensive means for obtaining the clearancedesired.

While the form of embodiment of the invention as'herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A rotary pump including a pumping chain ber wall, an impeller mounted within the cham- -ber wall, means for revolving the impeller eccentrically along the chamber wall, a pluralityof unsymmetrically positioned means with respect to the pumping chamber wall for provid- 5' ing a plurality -of sealsbetween the pumping chamber wall and the impeller to provide a plurality of pumping chambers of different size, a

section of the pumping chamber wall between two of the sealing means having a lesser clearance between said section and .the most eccentric portion of the impeller than between other portions of the wall and-said most ec'centricportion.

2. A rotary pump including a pumping chamber wall, an impeller mounted within the chamber wall, means for revolving the' impeller eccentrically along the chamber wall, a plurality of unsymmetrically positioned means with respect to the pumping chamber wall for providing 'a plurality of seals between the pumping chamber wall and the impeller to provide a plurality of pumping chambers of different size, a section of the pumping chamber wall between two of the sealing means being a separate piece from 5 the remainder of the wall and being movable in-- 1 dependently'from the remainder of the pumping chamber wall.

3. An eccentric type rotary pump including a pumping chamber wall, an impeller mounted It movable independently of t e remainder of the 9' chamber wall.- 4. An eccentric type rotary pump including a pumping chamber wall, an impeller mounted within the chamber wall, means for revolvin the impeller along the chamber wall, a plurality of divider blocks providing a plurality of seals between the pumping chamber wall and the impeller, said divider blocks being unsymmetrically positioned to provide pumping chambers of different size, said divider blocks being prevented from rotation with the impeller, a section of said chamber wall between twoof the blocks being a separate piece from the remainder of the wall, said section having a lesser clearance with respect to the impeller than the remainder of the chamber wall.

5. An eccentric type rotary pump including a pumping chamber wall, an impeller mounted within the chamber wall, means for revolving the impeller along the chamber wall, a plurality of divider blocks providing a plurality of seals between the pumping chamber wall and the impeller, said divider blocks being unsymmetrically positioned to provide pumping chambers of dif- 35 ferent size, said divider blocks being prevented from rotation with the impeller, a section of said chamber wall between two of the blocks being movable independently of the remainder of the chamber wall, and adjusting means for moving vtions of the chamber wall.

6. A rotary pump including a pumping cham- 41- meeeee he! wall, an impeller mounted within the chember wall, means for revolving the impeller elo the chamber wall, and means prevented fromo'otation with the impeller for providing it seal between the impeller and the well, said chamber well being provided with a lesser clearance between the most eccentric portion of the impeller 

